Traditionally, digitally controlled color printing capability is accomplished by one of two technologies. Both require independent ink supplies for each of the colors of ink provided. Ink is fed through channels formed in the printhead. Each channel includes a nozzle from which droplets of ink are selectively extruded and deposited upon a medium. Typically, each technology requires separate ink delivery systems for each ink color used in printing. Ordinarily, the three primary subtractive colors, i.e. cyan, yellow and magenta, are used because these colors can produce, in general, up to several million shades or color combinations.
The first technology, commonly referred to as “drop on demand” ink jet printing, selectively provides ink droplets for impact upon a recording surface using a pressurization actuator (thermal, piezoelectric, etc.). Selective activation of the actuator causes the formation and ejection of a flying ink droplet that crosses the space between the printhead and the print media and strikes the print media. The formation of printed images is achieved by controlling the individual formation of ink droplets, as is required to create the desired image. Typically, a slight negative pressure within each channel keeps the ink from inadvertently escaping through the nozzle, and also forms a slightly concave meniscus at the nozzle helping to keep the nozzle clean.
Conventional, droplet-on-demand ink jet printers utilize a heat actuator or a piezoelectric actuator to produce the ink jet droplet at orifices of a print head. With heat actuators, a heater, placed at a convenient location, heats the ink to cause a localized quantity of ink to phase change into a gaseous steam bubble that raises the internal ink pressure sufficiently for an ink droplet to he expelled. With piezoelectric actuators, a mechanical force causes an ink droplet to he expelled.
The second technology, commonly referred to as “continuous stream” or simply “continuous” ink jet printing, uses a pressurized ink source that produces a continuous stream of ink droplets. Traditionally. the ink droplets are selectively electrically charged. Deflection electrodes direct those droplets that have been charged along a flight path different from the flight path of the droplets that have not been charged. Either the deflected or the non-deflected droplets can he used to print on receiver media while the other droplets go to an ink capturing mechanism (catcher, interceptor, gutter, etc.) to be recycled or disposed. U.S. Pat. No. 1,941,001, issued to Hansell, on Dec. 26, 1933, and U.S. Pat. No. 3,373,437 issued to Sweet et al., on Mar. 12, 1968, each disclose an array of continuous ink jet nozzles wherein ink droplets to be printed arc selectively charged and deflected towards the recording medium.
Continuous ink jet printing systems use jetting modules to eject the droplet toward the print media. These units contain the electrical and fluid connections necessary for the jetting module to properly function. As can he expected, occasionally the jetting modules may need replacing due to normal wear and tear.
Commonly assigned U.S. patent application 2009/0295878 discloses a continuous inkjet printing system having a method and apparatus for replacing jetting modules. This disclosure is more than sufficient for some ink jet printers: however, in continuous ink jet printers having the jetting modules densely populated, additional complexities arise. For example, proper alignment of the print head to the deflection mechanism is even more technically demanding. Without belaboring each additional complexity, and as may be expected, it is sufficient to note that proper alignment of other components may also be more demanding.
Although the above described system is satisfactory, improvements in installing jetting modules for overcoming the above shortcomings are always desirable.